Led lighting apparatus and method for fabricating wavelength conversion member for use in the same

ABSTRACT

A method of forming a light-emitting diode (LED) lighting apparatus, including forming an LED on a printed circuit board, and forming a wavelength conversion member on the LED, the wavelength conversion member being spaced apart from the LED. Forming the wavelength conversion member includes transfer molding a wavelength conversion layer on a light-transmitting member, and disposing the wavelength conversion member on the LED, the wavelength conversion layer being disposed between the LED and the light-transmitting member.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/868,571, filed on Apr. 23, 2013, and claims priority from and thebenefit of Korean Patent Application No. 10-2012-0047882, filed on May7, 2012, each of which is hereby incorporated by reference for allpurposes as if fully set forth herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a light-emitting diode (LED) lightingapparatus and a method for fabricating a wavelength conversion memberwhich is spaced apart from an LED in the LED lighting apparatus andconverts a wavelength of light emitted from the LED.

2. Description of the Related Art

As light sources for illumination, fluorescent lamps and incandescentbulbs have been widely used. Incandescent bulbs have low efficiency andeconomic feasibility due to their high power consumption. For thisreason, the demand for incandescent bulbs tends to significantlydecrease. It is expected that such a decreasing trend will continue inthe future. On the contrary, since fluorescent lamps have about ⅓ ofpower consumption of incandescent bulbs, they are high-efficient andcost-efficient. However, since fluorescent lamps are blackened byapplication of high voltage, the lifespan of fluorescent lamps is short.In addition, fluorescent lamps are environmentally unfriendly becausethey use a vacuum glass tube into which mercury being a heavy metal isinjected together with argon gas.

Recently, the demand for LED lighting apparatuses has been rapidlyincreasing. LED lighting apparatuses have a long lifespan and are drivenwith low power. In addition, LED lighting apparatuses areenvironmentally friendly because they use no environmentally harmfulsubstances such as mercury. A typical LED lighting apparatus includes anLED module, and the LED module includes package-level or chip-levelLEDs, and a printed circuit board (PCB) on which the LEDs are mounted.Each of the LEDs includes an LED chip configured to emit light in aspecific wavelength range, and a wavelength conversion material (forexample, a phosphor) configured to generate desired color light,especially white light, by converting a wavelength of light emitted fromthe LED chip. Generally, the wavelength conversion material is includedin an encapsulation material covering the LED chip, or is directlyformed on the LED by conformal coating.

In the LED lighting apparatus, much heat is generated when the LEDS aresupplied with power and operated. This heat has a bad influence on thewavelength conversion material included in the encapsulation materialcovering the LED chip or directly formed on the LED chip. That is, theencapsulation material including the wavelength conversion material maybe separated from the surface of the LED chip by heat, and the originalcharacteristic of the wavelength conversion material may be changed byheat. Therefore, feature values, such as color coordinates or colortemperature of light generated by the LED lighting apparatus, maydeviate from an originally intended or designed range.

In this regard, there has been proposed an LED lighting apparatusconfigured such that an optical member or an optical cover spaced apartfrom LEDs includes phosphors. Since the optical member is spaced apartfrom the LEDs, the phosphors included in the optical member may not bebadly affected by heat generated from the LEDs. As a method of addingthe phosphors to the inside of the optical member, there are a method ofmolding an optical member with a resin material mixed with phosphors,and a method of coating a phosphor on one surface of an optical memberin a printing technique. Since the former method is limited to themolding technique using the resin material, it is difficult to apply toan optical member such as a glass. In addition, air bubbles may beformed within the optical member together with the phosphors. Accordingto the latter method, the phosphor layer is formed on one surface of theoptical member. The phosphor layer is formed with an uniform surface inthe early stage, but the surface of the phosphor layer may be rough astimes goes by. In worse cases, the phosphor layer may be separated fromthe surface of the optical member.

SUMMARY OF THE INVENTION

An aspect of the present invention is directed to provide a method forfabricating a wavelength conversion member reliably at low cost, inwhich the wavelength conversion member is used for an LED lightingapparatus and includes a uniform and dense wavelength conversion layeron at least one surface thereof.

Another aspect of the present invention is directed to provide an LEDlighting apparatus that can improve reliability by covering LEDs with awavelength conversion member including a uniform and dense wavelengthconversion layer on at least one surface thereof, and can always emitlight in an intended color coordinate or color temperature range, inspite of passage of time.

According to an aspect of the present invention, an LED lightingapparatus includes at least one LED, and a wavelength conversion memberspaced apart from the LED and configured to convert a wavelength oflight emitted from the LED. The wavelength conversion member includes alight-transmitting member, and a wavelength conversion layer formed onat least one surface of the light-transmitting member. The wavelengthconversion layer includes a resin and a phosphor, and is formed by atransfer molding.

According to one embodiment, the light-transmitting member may include aglass or a plastic material.

According to one embodiment, the light-transmitting member may includean uneven pattern. The uneven pattern may be formed in a region which iscovered with the wavelength conversion layer or a region which is notcovered with the wavelength conversion layer.

According to another aspect of the present invention, there is provideda method for fabricating a wavelength conversion member to be applied toan LED lighting apparatus. The method for fabricating the wavelengthconversion member includes: preparing a light-transmitting member;arranging a mold to cover one surface of the light-transmitting memberand; performing a transfer molding process to soften a solid moldingmaterial, including a phosphor and a resin, by heating and pressurizingthe solid molding material, and fill a gap between the mold and thelight-transmitting member with the softened molding material.

According to one embodiment, the mold may include a transfer port, and arunner extending from the transfer port to the gap. The transfer moldingprocess may include putting the solid molding material into the transferport, pressurizing the solid molding material with a plunger, andinjecting the softened molding material into the gap through the runner.

According to one embodiment, the transfer port and the runner may bedisposed in a region right above the light-transmitting member.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of an LED lighting apparatus accordingto an embodiment of the present invention.

FIG. 2 is a plan view illustrating a state in which a mold for molding awavelength conversion layer is disposed to cover one surface of alight-transmitting member.

FIG. 3 is a cross-sectional view taken along line I-I of FIG. 2.

FIGS. 4 and 5 are diagrams for describing a transfer molding process offorming the wavelength conversion layer on one surface of thelight-transmitting member by using the mold illustrated in FIGS. 2 and3.

FIG. 6 is a cross-sectional view of a wavelength conversion member inwhich the wavelength conversion layer is formed on one surface of thelight-transmitting member in the transfer molding process illustrated inFIGS. 4 and 5.

FIGS. 7A to 7D are cross-sectional views illustrating variousmodifications of the wavelength conversion member.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Exemplary embodiments of the present invention will be described belowin detail with reference to the accompanying drawings. These embodimentsare provided so that this disclosure will be thorough and complete, andwill fully convey the scope of the invention to those skilled in theart. The invention may, however, be embodied in many different forms andshould not be construed as being limited to the embodiments set forthherein. In the drawings, the widths, lengths and thicknesses of elementsmay be exaggerated for clarity. Throughout the drawings and description,like reference numerals will be used to refer to like elements.

FIG. 1 is a cross-sectional view of an LED lighting apparatus accordingto an embodiment of the present invention.

Referring to FIG. 1, the LED lighting apparatus 1 includes a pluralityof LEDs 2, and a wavelength conversion member 10 spaced apart from theLEDs 2 and covering top sides of the LEDs 2. The plurality of LEDs 2 aremounted on a printed circuit board (PCB). In addition, the PCB 3 isattached on a heat sink 5 and thermoconductively connected to the heatsink 5. The heat sink 5 may include a plurality of heat dissipation fins51. In addition, the LED lighting apparatus 1 may include a housing 6for accommodating the above-described LEDs 2 inside.

Although not illustrated, the LED lighting apparatus 1 may includecircuits and parts for driving the LEDs 2. The LED 2 may include an LEDchip and an encapsulation material encapsulating the LED chip. The LEDchip may be directly mounted on the PCB 3, or may be disposed on the PCB3 while being embedded in a package with lead terminals.

The LEDs 2 may include a GaN-based LED chip configured to emit bluelight, and an LED chip with a wavelength of about 430 μm to 470 μm,which includes an InGaN-based active layer. In addition, the wavelengthconversion member 10 includes a light-transmitting member 11 configuredto transmit light, and a wavelength conversion layer 12 formed on thesurface of the light-transmitting member 11. The wavelength conversionmember 10 includes a phosphor that converts blue light generated by theLED 2 into long-wavelength light, and the phosphor may be a yellowphosphor or a combination of a green phosphor and a red phosphor.

After light passes through the wavelength conversion member 10, thewavelength-converted long-wavelength light and thenon-wavelength-converted blue light may be mixed to generate whitelight. Since the phosphor within the wavelength conversion layer 12provided in the wavelength conversion member 10 is spaced apart from theLED 2, the characteristic or performance of the wavelength conversionmember 10 is not deteriorated by heat and/or light generated by the LED2.

The light-transmitting member 11 may be made of a plate type transparentglass or a plastic. However, the light-transmitting member 11 may bemade of light-transmitting materials other than glass. In addition, thewavelength conversion member 10 illustrated in FIG. 1 includes thewavelength conversion layer 12 only on the bottom surface of thelight-transmitting member 11, but the wavelength conversion layer 12 maybe formed only on the top surface of the light-transmitting member 11 ormay be formed on both the top surface and the bottom surface. Thewavelength conversion layer 12 is formed on the surface of thelight-transmitting member 11 to a predetermined thickness by thetransfer molding, and has a uniform phosphor distribution.

A method for fabricating the wavelength conversion member by forming thewavelength conversion layer 12 on one surface of the light-transmittingmember 11 by the transfer molding will be described in more detail.

FIG. 2 is a plan view illustrating a state in which a mold 80 isdisposed to cover one surface of the light-transmitting member 11 inorder for the transfer molding of the wavelength conversion layer 12(see FIG. 1). FIG. 3 is a cross-sectional view taken along line I-I ofFIG. 2.

Referring to FIGS. 2 and 3, the plate type mold 80 is disposed to coverone surface of the light-transmitting member 11 having an area equal toor smaller than that of the mold 80. In FIG. 2, the light-transmittingmember 11 is covered with the plate type mold 80 and is indicated by ahidden line. The plate type mold 80 includes one or more resin injectionportions 81. The mold 80 having an appropriate number of the resininjection portions 81 may be selected and used according to the area ofone surface of the light-transmitting member 11 or the area of thewavelength conversion layer 12 (see FIG. 1) formed on one surface of thelight-transmitting member 11 by the transfer molding. In this case, acircumference of a gap between the light-transmitting member 11 and theplate type mold 80 is filled.

The resin injection portion 81 includes a transfer port 812 and a runner814 having a cross-sectional area smaller than that of the transfer port812. The runner 814 extends from the transfer port 812 to a spacecovering one surface of the light-transmitting member 11, and mayinclude a runner of a narrow sense, a gate and/or a sprue. In thisembodiment, both the transfer port 812 and the runner 814 of the resininjection portion 81 are disposed in a region right above thelight-transmitting member 11.

In this embodiment, a gap between one surface of the light-transmittingmember 11 and the mold 80 facing each other becomes a space in which thewavelength conversion layer 12 is to be formed by the transfer molding.The runner 814 extends from the transfer port 812 to the space.

As illustrated in FIGS. 2 and 3, before the mold is arranged, a solidmolding material 70 mixed with a phosphor is prepared in a tablet form.The solid molding material 70 may be prepared in a tablet form bypressing a powder in which a phosphor and a powder-type resin areuniformly mixed. As the resin used herein as the solid molding material70, epoxy, especially epoxy molding compound (EMC) having excellentabsorption resistance, may be advantageously used.

FIGS. 4 and 5 are diagrams for describing the transfer molding processof forming the wavelength conversion layer on one surface of thelight-transmitting member by using the above-described mold.

Referring to FIGS. 4 and 5, under a high-temperature and high-pressurecondition, the transfer molding process is performed to inject thephosphor-containing resin into the gap (or space) between thelight-transmitting member 11 and the mold 80 through the resin injectionportion 81. More specifically, the tablet-shaped solid molding material70 is put into the transfer port 812 of the resin injection portion 81.While raising a temperature, a plunger 60 disposed in the transfer port812 moves vertically downward to pressurize the solid molding material70. The molding material 70, which is heated at a high temperature andpressurized at a high pressure, is softened into a gel phase or a liquidphase. The molding material 70 is densely filled into the gap betweenthe light-transmitting member 11 and the mold 80 through the runner 814and is then cured.

In this manner, the wavelength conversion layer 12 with the phosphorsuniformly distributed is formed on the surface of the light-transmittingmember 11 to a uniform thickness. In a case where the resin injectionportion 81 is provided in plurality (see FIG. 2), the plungers 60 areprovided as many as the number of the resin injection portions 81, andthe plungers 60 are vertically moved in synchronization. A heating unitsuch as a heater for heating the molding material 70 may be installed inthe plunger 60 or the mold 80.

FIG. 6 is a cross-sectional view of the wavelength conversion memberwith the wavelength conversion layer formed on one surface of thelight-transmitting member by the transfer molding step.

Referring to FIG. 6, the light-transmitting member 11 with thewavelength conversion layer 12 is separated from the mold 80. The curedresin r, which exists in the runner 814 (see FIGS. 2 to 5), may remainin the wavelength conversion layer 12. In this case, this resin r isremoved. As a result, it is possible to fabricate the wavelengthconversion member 10 in which the wavelength conversion layer 12 isuniformly formed on one surface of the light-transmitting member 11 bythe transfer molding.

The structure or shape of the mold 80 can be variously modified. Forexample, the transfer port 812 of the resin injection portion 81 may bedisposed at a position deviating from the light-transmitting member 11,and the runner 814 may extend to the lateral space of thelight-transmitting member 11 instead of the upper space of thelight-transmitting member 11.

Various modifications of the wavelength conversion members 10 accordingto the present invention are provided.

A wavelength conversion member 10 illustrated in FIG. 7A includes a pairof wavelength conversion layers 12 formed by a transfer molding on twoopposite surfaces of a light-transmitting member 11, that is, top andbottom surfaces thereof The pair of wavelength conversion layers 12 mayinclude the same phosphor or may include different phosphors. In awavelength conversion member 10 illustrated in FIG. 7B, a wavelengthconversion layer 12 is formed on one surface of a light-transmittingmember 11, and an uneven pattern 13 for light diffusion or scattering isformed on an opposite surface of the light-transmitting member 11. Theuneven pattern 13 diffuses or scatters light so thatwavelength-converted light and non-wavelength-converted light can bemixed more efficiently. Therefore, more uniform white light can beobtained. In a wavelength conversion member 10 illustrated in FIG. 7C,an uneven pattern 13 is formed on one surface of a light-transmittingmember 11, and a wavelength conversion layer 12 is formed by a transfermolding to cover the uneven pattern 13. A wavelength conversion member10 illustrated in FIG. 7D includes a curved portion, and a wavelengthconversion layer 12 is formed on the surface of the curved portion.

While the embodiments of the present invention have been described withreference to the specific embodiments, it will be apparent to thoseskilled in the art that various changes and modifications may be madewithout departing from the spirit and scope of the invention as definedin the following claims.

What is claimed is:
 1. A method of forming a light-emitting diode (LED)lighting apparatus, the method comprising: forming an LED on a printedcircuit board (PCB); and forming a wavelength conversion member on theLED, the wavelength conversion member being spaced apart from the LED,wherein forming the wavelength conversion member comprises: transfermolding a wavelength conversion layer on a light-transmitting member;and disposing the wavelength conversion member on the LED, thewavelength conversion layer being disposed between the LED and thelight-transmitting member.
 2. The method of claim 1, wherein transfermolding the wavelength conversion layer comprises: disposing a mold tocover a first surface of the light-transmitting member, a gap beingdisposed between the light-transmitting member and the mold; andperforming a transfer molding process, comprising: softening a solidmolding material, comprising a phosphor and a resin, by heating andpressurizing the solid molding material; and filling the gap between themold and the light-transmitting member with the softened moldingmaterial.
 3. The method of claim 2, wherein: the mold comprises at leastone resin injection portion comprising a transfer port and a runnerconnecting the transfer port and the gap; and transfer molding thewavelength conversion layer further comprises: disposing the solidmolding material in the transfer port; pressurizing the solid moldingmaterial with a plunger; injecting the softened molding material intothe gap, through the runner; and curing the molding material to form thewavelength conversion layer.
 4. The method of claim 3, wherein the moldcomprises an area equal to or greater than the area of thelight-transmitting member.
 5. The method of claim 4, further comprisingseparating the wavelength conversion member from the mold, beforedisposing the wavelength conversion member on the LED.
 6. The method ofclaim 1, further comprising forming a heat sink on an opposite surfaceof the PCB than the surface on which the LED is formed.
 7. The method ofclaim 6, wherein the heat sink comprises heat dissipation fins.
 8. Themethod of claim 1, further comprising forming a housing surrounding theLED.
 9. The method of claim 1, wherein the light-transmitting member isformed to have an uneven pattern in a portion on which the wavelengthconversion layer is disposed.
 10. The method of claim 1, wherein thelight-transmitting member is formed to have an uneven pattern in aportion on which the wavelength conversion layer is not disposed. 11.The method of claim 1, wherein the light-transmitting member comprises aglass or a plastic material.